1. Field of Invention
This invention relates to frames that are used to mount and to provide tension for flexible fabrics, such as artist's canvasses, silk screen, digital photographs, and the like. In particular this invention relates to special purpose corner clamps that are reusable to enable the attachment of the canvas to the stretcher bars.
2. Description of the Related Art
Most prior art stretchers are manufactured as standard dimension lengths with machined ends. These lengths are assembled into frames with interlocking corners. The canvas or material is stretched on this frame using stretching pliers and with staples on the side. Wedges can be inserted into the interlocking corners to expand the frame and tension the canvas. Stretcher bars of this type have a few disadvantages: When first assembled the stretcher bars must be squared and aligned by the user or the diagonals will be off, making subsequent framing difficult or impossible.
The stretching of the material on the stretcher bars requires the use of specific tools like stretching pliers and staple guns, both of which are costly and might not be available in the average consumer's household.
When stretching the material with pliers it is very difficult to apply an even tension along every side of the material and this can cause undue stress on the stretcher bars, quite often causing the frame to warp and the material to wrinkle.
This stretching system requires a fair amount of skill, strength and practice in order to get good results. Thus it is intimidating and not user friendly.
In this type of stretching system, the staples are normally placed on the side of the stretcher bars which make the side edges of the material unsightly.
The corners of the material must be folded and fastened on the sides, adding bulk and detracting further from the neat edge appearance of the finished product.
The sophisticated nature of the machined ends of the stretcher bars do not allow for resizing and therefore cannot be used if the dimensions of the material to be stretched does not fall within the standard sizes currently being manufactured.
Currently available stretcher bars allow for expansion with the use of wedge inserts into the interlocking corners. These inserts, however, are often missing from the corners making it impossible to retighten the corners without them.
A lot of material is wasted due to the fact that the stretching pliers need extra material around the frame to grab onto.
It is an object of the present invention to overcome the disadvantages described and provide a canvas stretching system which can be easily used by the professional or amateur framer.